CLOUD COVER |
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Fine: | Little cloud and no rainfall throughout the period. (Average cloud cover less than 2 oktas.) |
Sunny: | Bright sunshine most of the time with very little or no rainfall. (Average cloud cover less than 2 oktas, rainfall less than or equal a Trace) |
Fair: | Few low or medium clouds for most of the time and little or no rainfall. (Average cloud cover less than or equal 3 oktas, Rainfall less than or equal 0.01 inch or 0.254 mm.) |
Mainly/Mostly Fair: | More often fair than cloudy (including “fair with cloudy periods”), with no rainfall or only brief light showers. (Average cloud cover less than 5 oktas, rainfall less than or equal 0.02 inch or 0.508 mm) |
Mainly/Mostly Sunny: | More often sunny than fair (including “sunny with fair periods”) with little or no rainfall. (Average cloud cover less than 3 oktas, rainfall less than or equal 0.01 inch or 0.254 mm) |
Mainly/Mostly Cloudy: | Cloudy with fair breaks./td> |
Partly Cloudy: | No rainfall or only brief light showers. Total low and medium clouds less than or equal 3 oktas, high clouds more than 5 oktas, i.e. total clouds ranging from 3 to 6 oktas: rainfall less than or equal 0.03 inch or 0.762 mm. |
Increasing/Decreasing Cloudiness: | Amount of clouds generally increasing/decreasing to/from cloudy or overcast with only light showers or rainfall less than 0.05 inch or 1.27 mm. |
Cloudy: | Cloudy for most of the time. Generally lots of low or medium clouds. Average cloud cover equal 6 oktas, rainfall less than 0.05 inch or 1.27 mm |
Cloudy To Overcast: | Cloudy most of the time, otherwise overcast, with only light showers or rainfall. Average cloud cover equal 7 oktas, rainfall less than or equal 0.05 inch or 1.27 mm. |
Considerable Cloudiness/Overcast: | Overcast most of the time, otherwise cloudy. Average cloud cover greater than or equal 7 oktas, rainfall less than or equal 0.05 inch or 1.27mm |
RAINFALL |
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Showers: | Convective precipitation (not continuous) lasting from several minutes to one or two hours, with intensity from light-to-moderate to moderate-heavy |
Drizzle: | Precipitation from stratus clouds consisting of tiny droplets. |
Brief Showers: | Each shower lasting less than twenty minutes |
Squalls: | Light-to-moderate or moderate showers, each lasting less than half-an-hour preceded or accompanied by gusty winds |
Squally Showers: | Heavy showers or very heavy showers with thunderstorms and probably also lightning (used mainly during the day time) |
Heavy Squalls: | Moderate to heavy showers accompanied or proceeded by strong gusts |
Heavy Showers: | Convective precipitation lasting from half an hour to three hours with period(s) of heavy intensity |
Very Heavy Showers: | Convective precipitation lasting from half an hour to three hours with periods of very heavy or intense downpour |
Thunderstorms: | Moderate to heavy or heavy showers accompanied by thunder and/or lightning |
Heavy Thunderstorms: | Heavy or very heavy, or intense rainfall accompanied by thunder and lightning and possibly preceded or accompanied by gusty winds |
Very Heavy Thunderstorms: | Violent rainfall accompanied by gusty winds, thunder and lightning, likely causing some damage |
Light Rainfall: | Very light or light-to-moderate showers/rain over most areas |
Intermittent Rainfall: | Intermittent or continuous rainfall (from stratified clouds) intensity light-to-moderate to moderate-to- heavy unless otherwise indicated (by light, heavy or, exceptionally very heavy) |
SPATIAL COVERAGE |
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Isolated: | Occurring less than 10% – of the area |
Widely Scattered: | Occurring over 10% – 30% of the area |
Scattered: | Occurring over 30% – 60% of the area |
Widespread: | Many showers affecting most places. Occurring over 40% to 90% of the area |
Many/Several Places: | Occurring over 60% – 80% of the area |
Most Places: | Occurring over 80% – 95% of the area |
??? | Occurring over 85% – 100% of the area. e.g. cloudy with occasional showers |
Eastern Areas: | Surrey plus St Mary |
Western Areas: | Cornwall except Trelawny |
Central Areas: | Middlesex plus Trelawny but except St Mary |
Northeastern Areas: | Portland and St Mary |
Southeastern Areas: | St Thomas and St Andrew |
Northwestern Areas: | Hanover and St James |
Southwestern Areas: | Westmoreland and St Elizabeth |
Northcentral Areas: | St Ann and Trelawny |
Southcentral Areas: | St Catherine, Clarendon and Manchester |
Inland Areas: | Areas more than 3-miles away from the coast |
Hilly Areas: | All areas between 500 to 1500 ft |
Hilly Ground: | All areas above 1500 ft |
Mountain Areas: | Above 2000 ft |
Foothills: | All areas between 5 and 15 ft (rarely used) |
Coastal Areas: | Within 2 to 3 miles of seacoast |
Coastal Plains: | Below 500 ft and within 2 to 3 miles of seacoast |
Plains/Low-lying Areas: | Below 500 ft |
PROBABILITIES |
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No term used: | Over 85% average probability of occurrence |
Likely: | 50 to 85 % probability of occurrence |
Chance Of: | 15 to 50% average probability of occurrence of event which is unwanted by many users |
Slight Chance Of: | 5 to 15 % average probability of occurrence of an event which is unwanted by many users of the forecast (rarely used) |
Risk: | Same as chance but used only with unwanted events (e.g. “risk of very heavy thunderstorm” |
Slight Risk: | 5 to 15 % average probability of occurrence of unwanted event |
Percentage Probability: | This is reserved for the probability of occurrence at any one point and the term is therefore used in point forecasts but not used in the island forecast (e.g. 60% probability of showers) |
TIME |
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Dawn: | Morning/ evening twilight 5-7 a.m. / p.m. EST. |
Morning: | 6:00 a.m. to 12 noon |
Early Morning: | 6:00 to 8:00 a.m. |
Mid Morning: | 8:00 to 10:00 a.m. |
Forenoon: | 10:00am to noon |
Afternoon: | Noon to 6:00p.m. |
Early Afternoon: | Noon to 3:00p.m. |
Mid Afternoon: | 2:00p.m. to 4:00p.m. |
Late Afternoon: | 3:00p.m. to 6:00p.m. |
Evening: | 6:00p.m. to midnight |
Night: | 7:00pm to 5:00a.m. |
Brief: | Less than 20 minutes |
Prolonged: | More than 2 hours |
Occasional: | Occurring at least 3 times |